Document And Entity Information - shares	3 Months Ended
	Jun. 30, 2024	Aug. 08, 2024
Document Information [Line Items]
Entity Central Index Key	0001444192
Entity Registrant Name	Acasti Pharma Inc.
Amendment Flag	false
Current Fiscal Year End Date	--03-31
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2024
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
Document Transition Report	false
Securities Act File Number	001-35776
Entity Incorporation, State or Country Code	Z4
Entity Tax Identification Number	98-1359336
Entity Address, Address Line One	103 Carnegie Center Suite 300
Entity Address, City or Town	Princeton
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08540
City Area Code	818
Local Phone Number	839-4378
Title of 12(b) Security	Common Shares, no par value per share
Trading Symbol	ACST
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		10,139,861
Former Address [Member]
Document Information [Line Items]
Entity Address, Address Line One	2572 boul. Daniel-Johnson, 2nd Floor
Entity Address, City or Town	Laval
Entity Address, State or Province	QC
Entity Address, Country	CA
Entity Address, Postal Zip Code	H7T 2R3